Decorative molding techniques such as in-mold transfer, in-mold lamination and vacuum pressure molding lamination have been used for home electric appliances, auto interior parts and miscellaneous goods, and application ranges thereof are widely expanding due to growing environmental awareness and advances in technical innovations in recent years. Decorative molding films obtained by carrying out printing, shaping or metal deposition on a film are used for decorative molding. Acrylic films, PET films and polycarbonate films have been used as base films for these.
Characteristic properties required for the base films include thermoformability that ensures a target shape to be accurately transferred, solvent resistance required for the decoration of the surface of a film such as printing, surface hardness, heat resistance, transparency and weather resistance. However, there is no substrate which satisfies all the above requirements, and the above films have been used according to purpose while they sustain problems.
For example, acrylic films are often used for the purpose of the present invention due to their excellent trimming properties in a specific decorative molding method since they have excellent transparency and weather resistance and such high brittleness that they are easily broken. However, there is limitation to the use of the films for purposes in which high heat resistance is required, and it is difficult to use the acrylic films in fields in which high heat resistance is required while cracking ease at the time of trimming is retained.
In the case of polycarbonate films, although they have high heat resistance, they have higher ductility than the acrylic films so that they are hardly broken, whereby they are inferior in trimming properties.
As one of measures for improving the characteristic properties of the substrate, there is proposed a multi-layer film having an acrylic resin layer on at least one side of a polycarbonate resin layer (Patent Documents 1 to 10).
This multi-layer film improves the heat resistance of the acrylic film and also the surface hardness, solvent resistance and weather resistance of the polycarbonate film. Thus, it is aimed to obtain good balance among properties by making use of the advantages of these films. However, this multi-layer film is not satisfactory in terms of trimming properties and surface hardness as compared with an acrylic single-layer film, and its thermoformability and appearance and transparency after molding have often come into question.
Although various studies have been made to improve the characteristic properties of the multi-layer film as a substrate for a decorative molding film from the viewpoints of the improvement of raw materials and the constitution of a laminate, the multi-layer film is not satisfactory yet and the further improvement of the film is desired.
(Patent Document 1) U.S. Pat. No. 3,457,514
(Patent Document 2) U.S. Pat. No. 3,489,972
(Patent Document 3) U.S. Pat. No. 3,904,262
(Patent Document 4) JP-A 2005-231257
(Patent Document 5) JP-A 2005-219330
(Patent Document 7) JP-A 2009-172953
(Patent Document 8) JP-A 2009-234183
(Patent Document 9) JP-A 2009-234184
(Patent Document 10) JP-A 2009-248363